The present invention relates to magnetic recording and reproducing devices and methods, and more particularly to a magnetic recording and reproducing device and method which records high-quality digital audio signals in a multiplexed manner while maintaining the compatibility with the existing systems.
As disclosed in Unexamined Japanese patent Publication JP-A Heisei 1-105301, a conventional magnetic recording and reproducing device multiplexes a frequency-modulated audio signal and a quadrature phase shift keyed digital audio signal in a frequency divisional manner, further superimposes a high frequency bias signal on them, records those signals into a deep portion of a magnetic layer of a magnetic tape with a rotational audio head and superimposes a video signal with a rotational video head which is different in azimuth angle from the rotational audio head into an upper surface portion of the magnetic layer above the track formed by that recording.
However, the conventional technique does not allow for the relationship between the carrier frequency fp of the digital audio signal and the frequency fB of the high frequency bias signal. Thus, it has the problem that a 5th-order distortion (4.times.fp-fB) component due to cross modulation of the digital audio signal and bias signal adversely influences the FM audio signal and video signal.
The conventional technique does not allow for the magnetic gap length of the rotational audio head either and has a problem with ensuring a reproduced output level of the digital audio signal.
The magnetic gap length of the existing rotational audio heads is about 1.1-1.3 .mu.m, which allows for only recording and reproducing the FM audio signal. If the digital audio signal is recorded and reproduced using that magnetic gap length, the reproduced output of the digital audio signal is reduced due to so-called gap loss and hence a required C/N (Carrier to Noise) ratio cannot be ensured.
It is an object of the present invention to provide a magnetic recording and reproducing method and device which eliminates the drawbacks of the conventional techniques, eliminates adverse influence of distortion components due to cross modulation of the digital audio signal and bias signal on the FM audio signal and video signal, and ensures the reproduced output level of the digital audio signal.